78 BRITISH OOLITIC AND LI ASIC BRACHIOPODA. 



resemblance this shell presents to a dog's head. Most Palaeontologists, singularly enough, 

 have not coincided with Mr. Richard's views, for we see Bronn and others placing Ter. 

 bidens with its variation T. biplicata, and T. cynocephala, in one species, (Index Pal., 

 p. 1251.) Mr. Woodward fully understood the necessity of adopting a distinct name 

 for the shell under notice, and in the collection of the British Museum made use of 

 Mr. Richard's name. In 1828 Young and Bird figured a shell under the name of 

 Ter. lineata; but, from want of description and the incorrect illustration, it is impossible to 

 decide as to the shell intended. Through the kindness of Mr. Riply, of Whitby, I was able 

 to convince myself that both T. bidens, and cynocephala, occur in Yorkshire, but in different 

 beds, and that both species seem perfectly distinct. R. cynocephala, as we have above 

 remarked, has for general character the bidentation of its elevated mesial fold; but in some 

 rare cases, the bidentation is replaced by one single elevated plait, as in R. acuta (see fig. 10) ; 

 and in other similarly rare exceptions, instead of the single bidentation, that portion is 

 tridentated, as in fig. 12. I am indebted to Messrs. Lycett and Woodward for specimens 

 confirming this fact in the most positive manner. 



R. cynocephala is found in the inferior Oolite of Minchinhampton, Dinnington, 

 Yorkshire, &c. ; on the continent it was discovered by Mr. Richard, in the inferior Oolite of 

 Bourmont. 



Figs. 10, 11, 12, are drawn from specimens in the collection of the British Museum, 

 and in that of Mr. Lycett. 



71. Rhynchonella variabilis, Schloth., Sp. Plate XVI, figs. 1 — 6, and Plate XV, 



figs. 8—10. 



Terebratulites variabilis, Schlotheim, 1813. Beitrage zur Naturgeschite der 



Versteinerungen in Leonhard's Mineral Tashent, 

 vol. vii, p. i, fig. 4. 



— triplicata, Phillips, 1835. Illustrations of the Geology of Yorkshire, 



Part I, p. 157, pi. xiii, fig. 22. 



— bidens, ibid., pi. xiii, fig. 24. 



— triplicata, V. Buck, 1838. Mem. Soc. Geol. de France, vol. iii, 



Ire ser., p. 140, pi. xiv, fig. 9. 



— variabilis, ibid., pi. xiv, fig. 10. 



— triplicata, Beshayes, 1836. Nouv. Ed. de Lamarck, p. 353. 



— variabilis, Pusch. Polens Palaeontologie, 1837, p. 11, pi. iii, fig. 2. 



— triplicata and bidens. Deslong champs, 1837. Soc. Linn, de 



Normandie, p. 30. 



— — Morris. Catalogue, 1843. 



— — Tennant, 1847. A Strat. List of British Fossils, p. 74. 



— — C. Rouillier and A. Fossinsky, 1847. Etudes Prog, sur 



la Pal. des Env. de Moscou, No. 11, tab. b, fig. 17- 

 __ _ Bronn, (pars) 1848. Index Pal., p. 1254. 



Rrynchonella variabilis, D'Orbiffny. Prodrome, 1849, vol. i, p. 239. 



